Heart valve stiffening ring



FIG. 1 is a top perspective view of a heart valve stiffening ring showing my new design;

FIG. 2 is a top plan view of the heart valve stiffening ring of FIG. 1;

FIG. 3 is a bottom plan view of the heart valve stiffening ring of FIG. 1;

FIG. 4 is a side elevational view of the heart valve stiffening ring of FIG. 1; and,

FIG. 5 is an elevational view of the heart valve stiffening ring showing an opposite side from that illustrated in FIG. 4.

The broken line showing of the heart valve annular channel shaped body in FIG. 1 is for illustrative purposes only and forms no part of the claimed design. 

The ornamental design for a heart valve stiffening ring, as shown and described. 